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Old 13th February 2012, 20:44   #136
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Default Re: Driving all four wheels: how is it done?

Back to back posts. Addressing very different issues.

Quote:
Originally Posted by Crazy4Power View Post
secondly is it possible to change the clutch part in XUV (highlighted with circle) with a transfercase, matching the same gear ratio; offcourse after warranty period. And also what will happen if the gear ratio of front and rear axle is different in offroading condition, considering that front on normal gear ratio & rear at lower gear ratio.
Look up the Jensen FF system, and 'bump' modes of viscous couplings.
Don't get your thought process re: xfer cases.

Quote:
Originally Posted by ex670c View Post
Pic#1.
The transverse mounted engine drives the Cluth Assy and Gear Box which drives a large (almost 4:1) Helical Gear mounted on a Hypoid Gear Assy (Spider Gears) which provide for the Differential Action.
Hypoid is something else.
The RHS Drive Shaft has a Crown & Pinion gear assy to take drive off to the Rear Differential.
No. Concentric shafts.


Pic#3.
The Crown & Pinion Assy connects to the rear differential, through a Clutch Pack, this indicates the vehicle is not a real AWD, and the Rear Differential will engage when there is sufficient slippage leading to the Diff Assy oil heating up and expanding the Clutch plates; thereby engaging the Rear Diff & Axles.
A speed differential will always have a torque transfer. If properly designed, heating up (and expansion) of the working fluid can be used to lock up the clutch.


If the system is efficient enough and generates enough torque and if it can reach the wheel, definitely the vehicle can move over sand, mud, dunes & steep climbs.
Normally in this type of system, torque transfer varies, out of control of the driver. In a situation where traction is at a premium for any significant distance, this type of vehicle moves in bursts.
Quote:
Originally Posted by Crazy4Power View Post
YES they have AWD lock selector button, which can be activated to forcibly bring the car to AWD. I think this is a big plus to avoid the unnecessary clutch slippage.
I see no mechanism for external control of the clutch pack.
So need to know more of the MM system.

Quote:
Originally Posted by Endeavour333 View Post
Arka this is the kind of LSD I had associated with a "clutch pack" LSD. Like you said above, I thought they required a lot of wheel speed difference to engage and transfer torque.

So there are 3 types of clutch pack LSDs?
1) conical
2) normal
(both conical and normal are engaged at all times acting like a locker until wheel speed differential forces are large enough to slip the clutch)
If there is a speed differential, the clutch is slipping.
3) oil based clutch pack LSD like in the XUV: high wheel speed differential required to heat up oil to make clutch places press against each other to transfer torque.
That is a special mode. Otherwise a speed differential means a transfer of torque.
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Old 13th February 2012, 21:13   #137
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Default Re: Driving all four wheels: how is it done?

Quote:
Originally Posted by Endeavour333 View Post
Great technical thread! I love this stuff.

Endeavour: Part-time 4x4 with Center Transfer case, Torsen LSD in the rear - Meaning that you would need to lose traction in 3 wheels to come to a halt. Even if one rear wheel is in the air you can use the throttle-brake technique to get some power to the rear wheel that has traction to get out.
Vish - We will test it this weekend - 3 wheels in the air and loosing traction as well as the method to regain the same

Quote:
Originally Posted by Endeavour333 View Post
With a torsen LSD, when one wheel is in the air, 0 torque goes to the wheel that has traction. The trick to getting power to the other wheel on the ground is to apply the hand brake to provide some resistance to the wheel in the air. The torsen LSD multiplies whatever resistance the handbrake puts on the wheel in the air 3 to 5 times (depending on some ratio of the torsen) and transfers that torque to the wheel that has grip. Works very very well on the road.
This Handbrake / Brake technique works on open diff vehicles too
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Old 14th February 2012, 03:19   #138
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Originally Posted by headers

Vish - We will test it this weekend - 3 wheels in the air and loosing traction as well as the method to regain the same

This Handbrake / Brake technique works on open diff vehicles too
Works on open diff too??? But on torsen the torque gets multiplied from one wheel to the other.

Also, won't be able to make it this weekend sadly as I'll be traveling to Sri Lanka. Hopefully by the next OTR I would have got myself some nice MT tyres though.
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Old 14th February 2012, 19:04   #139
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Default Re: Driving all four wheels: how is it done?

Quote:
Originally Posted by Endeavour333 View Post
Also, won't be able to make it this weekend sadly as I'll be traveling to Sri Lanka. Hopefully by the next OTR I would have got myself some nice MT tyres though.
Too bad - I was hoping to see the Endy do some stunts - Maybe it would with MT tyres - Go for 35
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Old 17th February 2012, 15:39   #140
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Default Re: Driving all four wheels: how is it done?

Quote:
Originally Posted by Endeavour333 View Post
With a torsen LSD, when one wheel is in the air, 0 torque goes to the wheel that has traction. The trick to getting power to the other wheel on the ground is to apply the hand brake to provide some resistance to the wheel in the air. The torsen LSD multiplies whatever resistance the handbrake puts on the wheel in the air 3 to 5 times (depending on some ratio of the torsen) and transfers that torque to the wheel that has grip. Works very very well on the road. Lots of sports cars use torsen LSDs including the Lexus LFA. But when Offroad, their use is sort of limited. The only places where a torsen will help you Offroad is when you are in slush or sand (both wheels are making contact).

Hope this has helped your understanding.
First of all, thank you every one for this particular thread. I W'really love team-bhp.... it gives me mental food

@Endeavour333, the work of LSD is to limit the slip (hence the name - Limited Slip Differential) at the slipping wheel and to transfer the torque to the wheel with more traction.

If one wheel is in the air, LSD will limit the slip at the slipping wheel & further, transfer higher torque to the other wheel with traction - the LSD is meant for this purpose only. In Fortuner, as you know, we have Torque Sensitive limited Slip Differential.

What you have mentioned happens in two wheel drive with open diffrential (with NO LSD). If one wheel is in air, the torque will follow the path of least resistance and will go to the wheel in air (0 torque). Thus the other wheel with traction will get no power at all. Here, to counter this unwanted situation, you should apply hand brake / brake technique so that the vehicle is virtually fooled and you get, to get, the torque to the wheel with traction and the vehicle moves out.
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Old 17th February 2012, 16:00   #141
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Default Re: Driving all four wheels: how is it done?

Devrishi, you are describing clutch type or viscous type LSD. Endeavour333 was describing torsen type LSD, and his description is correct on that.
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Old 17th February 2012, 17:55   #142
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Default Re: Driving all four wheels: how is it done?

Quote:
Originally Posted by Devrishi View Post
If one wheel is in air, the torque will follow the path of least resistance and will go to the wheel in air (0 torque). Thus the other wheel with traction will get no power at all. Here, to counter this unwanted situation, you should apply hand brake / brake technique so that the vehicle is virtually fooled and you get, to get, the torque to the wheel with traction and the vehicle moves out.
This technique is correct and can be used in Open Diff vehicles to get out of sticky situations.
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Old 17th February 2012, 18:58   #143
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Default Re: Driving all four wheels: how is it done?

Hello everyone,
This is a very interesting and informative thread.
My humble apologies for going OT with this only question. Will appreciate feedback and answers.
My Safari 4x4 will be out of warranty after 1 month and I plan to make a SPIDEY(almost) of it and I will start a separate thread in the 4x4 section for guidance.
However here goes my small question.

The Safari 4x4 LSD is honestly not worth a fig for serious offroad activity.
I believe the Safari 4x4 comes with a Dana 44 LSD at the rear.
I found this during my online research.

Installing the POWERTRAX No-Slip Locker

This fits a Dana 44 Diff.
Can this be installed in a Safari?
Can someone explain or advise if this will be better than the existing LSD ?
I do not have specifications of the front diff.. Can an LSD be fitted in the front differential too?
Does anyone have specifications for the front Differential of the Safari 2.2 ?

OR

Can manual lockers be fitted on the Safari front and rear ?
If yes, which ones ?

Regards,
Jay
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Old 17th February 2012, 19:43   #144
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Default Re: Driving all four wheels: how is it done?

Quote:
Originally Posted by jaysmokesleaves View Post
I believe the Safari 4x4 comes with a Dana 44 LSD at the rear.

Installing the POWERTRAX No-Slip Locker

This fits a Dana 44 Diff.
Can this be installed in a Safari?
Can someone explain or advise if this will be better than the existing LSD ?
I do not have specifications of the front diff.. Can an LSD be fitted in the front differential too?
Does anyone have specifications for the front Differential of the Safari 2.2 ?

OR

Can manual lockers be fitted on the Safari front and rear ?
If yes, which ones ?
Hi,
1. Yes
2. Yes
3. A Locker is better than a LSD in OTR situations.
4. You ought to check with TML about the front diff of the safari 2.2

5. Can you elaborate what manual lockers are?
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Old 17th February 2012, 22:11   #145
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Default Re: Driving all four wheels: how is it done?

Quote:
Originally Posted by Devrishi View Post
In Fortuner, as you know, we have Torque Sensitive limited Slip Differential.
Indian Fortuner has a LSD?

Quote:
Originally Posted by headers View Post
This technique is correct and can be used in Open Diff vehicles to get out of sticky situations.
The standard open diff sends equal torque to both wheels. Increase the torque requirement of the free wheel, and the other wheel will also get the same torque. But i think most of that increased torque will be used up overcoming the now applied brakes.
Should be far far more effective with a Torsen. (No personal experience)

Regards
Sutripta
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Old 17th February 2012, 22:45   #146
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Default Re: Driving all four wheels: how is it done?

^^^
Addition. Meant Rear LSD. Not central.

Regards
Sutripta
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Old 17th February 2012, 22:46   #147
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Default Re: Driving all four wheels: how is it done?

Quote:
Originally Posted by Devrishi View Post
If one wheel is in the air, LSD will limit the slip at the slipping wheel & further, transfer higher torque to the other wheel with traction - the LSD is meant for this purpose only.
You are describing clutch/viscous type LSD, which is not found in Endy/Fortuner/GV.

Quote:
Originally Posted by Devrishi View Post
In Fortuner, as you know, we have Torque Sensitive limited Slip Differential.
Quote:
Originally Posted by Sutripta View Post
Indian Fortuner has a LSD?
Only in the center diff. So it doesn't apply to the scenario he was describing.

Quote:
Originally Posted by Devrishi View Post
What you have mentioned happens in two wheel drive with open diffrential (with NO LSD). If one wheel is in air, the torque will follow the path of least resistance and will go to the wheel in air (0 torque). Thus the other wheel with traction will get no power at all.
This does happen with torsen LSD, just like open diff.

Quote:
Originally Posted by Devrishi View Post
Here, to counter this unwanted situation, you should apply hand brake / brake technique so that the vehicle is virtually fooled and you get, to get, the torque to the wheel with traction and the vehicle moves out.
Quote:
Originally Posted by headers View Post
This technique is correct and can be used in Open Diff vehicles to get out of sticky situations.
Quote:
Originally Posted by Sutripta View Post
The standard open diff sends equal torque to both wheels. Increase the torque requirement of the free wheel, and the other wheel will also get the same torque. But i think most of that increased torque will be used up overcoming the now applied brakes.
Basically you should be toe-heeling the A and B pedal. The brake should merely slow down the spinning wheel, not stop it from turning.

Quote:
Originally Posted by Sutripta View Post
Should be far far more effective with a Torsen. (No personal experience)
Yup, thanks to the multiplier effect.
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Old 17th February 2012, 22:51   #148
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Default Re: Driving all four wheels: how is it done?

Quote:
Originally Posted by Samurai View Post
Basically you should be toe-heeling the A and B pedal. The brake should merely slow down the spinning wheel, not stop it from turning.
Hi,
Have used it often, and it does work. But logically should not work too well.
Wish I had a means of measuring out the forces.
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Old 18th February 2012, 18:09   #149
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Default Re: Driving all four wheels: how is it done?

I've made an excel file to help people understand the behavior of the different types of LSDs in different conditions. I have attached an image of the file and also the excel file itself for people to make changes or additions to it if need be. I was thinking of including rows for performance in sand, slush, relatively high traction climbs, uneven ground, etc. But thought that what I have done so far would give people a good understanding. Hope it helps.

A side note: For vehicles with a center diff and no rear LSD, locking the central diff would just make it act like an open diff vehicle like a Jeep.

Some other interesting questions I had:
1) To make the Throttle-Brake technique with a Torsen LSD work should you brake brake with wheels stopped and then accelerate while slowly releasing brake or should you apply brakes to slipping wheels to add resistance and transfer torque?

2) Applying brakes on rear axle while transfercase locked same as applying brake on al wheels? Because the front and rear axles are locked, braking wheels on one axle applies brakes on the other other axle as well correct? Therefore: Applying rear Hand brake will not only brake rear wheels but also front wheels? And applying the normal brakes (which are biased toward the front) will also brake the rear wheels right? So for a rear Torsen LSD at the rear does it make a difference if we apply hand brake or normal brake? I dont think so but would like to hear what others think.

Love the discussion. Please keep sharing the knowledge.
Attached Thumbnails
Driving all four wheels: how is it done?-diff-behavior.jpg  

Attached Files
File Type: xlsx LSD Behavior.xlsx (12.4 KB, 254 views)

Last edited by Endeavour333 : 18th February 2012 at 18:35.
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Old 18th February 2012, 19:03   #150
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Default Re: Driving all four wheels: how is it done?

Quote:
Originally Posted by Endeavour333 View Post
A side note: For vehicles with a center diff and no rear LSD, locking the central diff would just make it act like an open diff vehicle like a Jeep.
Hi Vishnu,

Based on the Centre Diff analogy, M&M Jeeps have a permanently locked Centre Diff.

Regards,

Arka
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